From: Jason Gunthorpe <jgg@ziepe.ca>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Alexey Kardashevskiy <aik@amd.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, linux-pci@vger.kernel.org,
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Jiri Pirko <jiri@resnulli.us>
Subject: Re: [PATCH kernel 6/9] x86/dma-direct: Stop changing encrypted page state for TDISP devices
Date: Fri, 27 Feb 2026 20:06:30 -0400 [thread overview]
Message-ID: <20260228000630.GN44359@ziepe.ca> (raw)
In-Reply-To: <d8102507-e537-4e7c-8137-082a43fd270d@arm.com>
On Wed, Feb 25, 2026 at 05:08:37PM +0000, Robin Murphy wrote:
> I guess this comes back to the point I just raised on the previous patch -
> the current assumption is that devices cannot access private memory at all,
> and thus phys_to_dma() is implicitly only dealing with the mechanics of how
> the given device accesses shared memory. Once that no longer holds, I don't
> see how we can find the right answer without also consulting the relevant
> state of paddr itself, and that really *should* be able to be commonly
> abstracted across CoCo environments.
Definately, I think building on this is a good place to start
https://lore.kernel.org/all/20260223095136.225277-2-jiri@resnulli.us/
Probably this series needs to take DMA_ATTR_CC_DECRYPTED and push it
down into the phys_to_dma() and make the swiotlb shared allocation
code force set it.
But what value is stored in the phys_addr_t for shared pages on the
three arches? Does ARM and Intel set the high GPA/IPA bit in the
phys_addr or do they set it through the pgprot? What does AMD do?
ie can we test a bit in the phys_addr_t to reliably determine if it is
shared or private?
> > pci_device_add() enforces the FFFF_FFFF coherent DMA mask so
> > dma_alloc_coherent() fails when SME=on, this is how I ended up fixing
> > phys_to_dma() and not quite sure it is the right fix.
Does AMD have the shared/private GPA split like ARM and Intel do? Ie
shared is always at a high GPA? What is the SME mask?
Jason
next prev parent reply other threads:[~2026-02-28 0:06 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-25 5:37 [PATCH kernel 0/9] PCI/TSM: coco/sev-guest: Implement SEV-TIO PCIe TDISP (phase2) Alexey Kardashevskiy
2026-02-25 5:37 ` [PATCH kernel 1/9] pci/tsm: Add TDISP report blob and helpers to parse it Alexey Kardashevskiy
2026-02-25 6:16 ` dan.j.williams
2026-02-25 10:10 ` Arnd Bergmann
2026-02-26 0:09 ` Alexey Kardashevskiy
2026-02-26 2:34 ` dan.j.williams
2026-02-26 3:49 ` Alexey Kardashevskiy
2026-02-26 21:08 ` dan.j.williams
2026-02-25 5:37 ` [PATCH kernel 2/9] pci/tsm: Add tsm_tdi_status Alexey Kardashevskiy
2026-02-25 6:33 ` dan.j.williams
2026-02-25 23:42 ` Alexey Kardashevskiy
2026-03-02 6:58 ` Aneesh Kumar K.V
2026-02-25 5:37 ` [PATCH kernel 3/9] coco/sev-guest: Allow multiple source files in the driver Alexey Kardashevskiy
2026-02-25 5:37 ` [PATCH kernel 4/9] dma/swiotlb: Stop forcing SWIOTLB for TDISP devices Alexey Kardashevskiy
2026-02-25 16:30 ` dan.j.williams
2026-02-25 18:00 ` Robin Murphy
2026-02-25 20:57 ` dan.j.williams
2026-02-28 0:28 ` Jason Gunthorpe
2026-03-02 23:53 ` dan.j.williams
2026-03-03 0:19 ` Jason Gunthorpe
2026-03-03 0:29 ` dan.j.williams
2026-03-03 12:43 ` Jason Gunthorpe
2026-03-04 6:45 ` Alexey Kardashevskiy
2026-03-04 12:43 ` Jason Gunthorpe
2026-03-25 10:42 ` Alexey Kardashevskiy
2026-02-25 16:48 ` Robin Murphy
2026-02-26 0:09 ` Alexey Kardashevskiy
2026-03-02 7:54 ` Aneesh Kumar K.V
2026-02-25 5:37 ` [PATCH kernel 5/9] x86/mm: Stop forcing decrypted page state " Alexey Kardashevskiy
2026-02-25 16:51 ` dan.j.williams
2026-02-25 5:37 ` [PATCH kernel 6/9] x86/dma-direct: Stop changing encrypted " Alexey Kardashevskiy
2026-02-25 17:08 ` Robin Murphy
2026-02-25 21:35 ` dan.j.williams
2026-02-26 6:22 ` Alexey Kardashevskiy
2026-02-28 0:06 ` Jason Gunthorpe [this message]
2026-03-02 0:01 ` Alexey Kardashevskiy
2026-03-02 0:35 ` Jason Gunthorpe
2026-03-02 5:26 ` Alexey Kardashevskiy
2026-03-02 13:35 ` Jason Gunthorpe
2026-03-03 8:19 ` Alexey Kardashevskiy
2026-03-03 12:15 ` Jason Gunthorpe
2026-02-25 5:37 ` [PATCH kernel 7/9] coco/sev-guest: Implement the guest support for SEV TIO (phase2) Alexey Kardashevskiy
2026-02-25 6:00 ` Borislav Petkov
2026-02-26 3:39 ` Alexey Kardashevskiy
2026-02-26 19:52 ` Borislav Petkov
2026-02-25 5:37 ` [PATCH kernel 8/9] RFC: PCI: Avoid needless touching of Command register Alexey Kardashevskiy
2026-02-26 0:24 ` Bjorn Helgaas
2026-02-26 5:58 ` Alexey Kardashevskiy
2026-02-26 0:34 ` dan.j.williams
2026-02-25 5:37 ` [PATCH kernel 9/9] pci: Allow encrypted MMIO mapping via sysfs Alexey Kardashevskiy
2026-03-02 8:20 ` Aneesh Kumar K.V
2026-03-02 8:59 ` Alexey Kardashevskiy
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